Water vapor transmission and moisture accumulation in polyurethane and polyisocyanurate foams

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Proceedings titleASTM Special Technical Publication
ConferenceWater Vapor Transmission through Building Materials and Systems : Mechanisms and Measurement : Symposium: 10 December 1987, Bal Harbour, FL, USA
Pages6372; # of pages: 10
Subjectthermal insulation; heat transfer; expanded plastics; laboratory tests; water vapor transmission; testing; water vapor permeance; thermal gradient; polyurethane foam; polyisocyanurate foam; moisture accumulation; vapour; modified cup method; dry cup method; temperature gradient method; Hygrothermal properties; Cellular plastics (plastic foam)
AbstractWater vapor transport through rigid polyurethane and polyisocyanurate foams was investigated using three test methods--two under isothermal conditions and one in the presence of a thermal gradient. All three methods yielded water vapor transmission coefficients of the materials. It is observed that the magnitude of the coefficients increases rapidly with temperature above 20 deg. C. In one of the isothermal methods called a modified cup method, developed at the Institute for Research in Construction, only the temperature has to be controlled and this is considered a definite advantage over the other method, ASTM Test Methods of Water Vapor Transmission of Materials, (E 96-80) dry cup method, in which both temperature and relative humidity are to be controlled. Further, the modified cup method also allows the determination of moisture accumulated in the test specimen during moisture transport. It was conclusively shown that during isothermal transport processes no moisture accumulates in either the polyurethane or the polyisocyanurate specimens. The accumulation and distribution of moisture in the presence of a thermal gradient was also investigated. Contrary to the isothermal process, the moisture transport in the presence of a thermal gradient acting in the same direction as the vapor pressure gradient results in the accumulation of large quantities of water in the foams. This phenomenon may be partly attributed to the temperature dependence of the water vapor transmission coefficients.
Publication date
PublisherPhiladelphia, PA. : The American Society for Testing and Materials
AffiliationNRC Institute for Research in Construction; National Research Council Canada
Peer reviewedYes
NRC number30890
NPARC number20375414
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Record identifier7d904a66-340e-463f-a4c5-ec2eca69583f
Record created2012-07-23
Record modified2016-05-09
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